rpp/src/drv/dac.c

   1 /* Copyright (C) 2012-2015 Czech Technical University in Prague
   2  *
   3  * Authors:
   4  *     - Michal Horn
   5  *     - Carlos Jenkins <carlos@jenkins.co.cr>
   6  *
   7  * This document contains proprietary information belonging to Czech
   8  * Technical University in Prague. Passing on and copying of this
   9  * document, and communication of its contents is not permitted
  10  * without prior written authorization.
  11  *
  12  * File : dac.c
  13  * Abstract:
  14  *     RPP driver implementation for DAC.
  15  *
  16  * References:
  17  *     None
  18  */
  19
  20
  21 #include "drv/dac.h"
  22 #include "drv/port.h"
  23
  24 #define DAC_PIN_NUM     4
  25
  26
  27 /**
  28  * Pin status for each DAC pin, the structure of each field is defined
  29  * as spi command structure.
  30  *
  31  * See mcp4922.pdf p. 24
  32  * Options:
  33  *   Bit 13: Output Gain Selection bit set = 1x (VOUT = VREF * D/4096)
  34  *   Bit 15: DACA (0) or DACB (1) Selection bit.
  35  *
  36  */
  37 static uint16_t dac_pin_status[DAC_PIN_NUM] = {
  38         (_BV(13)          ),
  39         (_BV(13) | _BV(15)),
  40         (_BV(13)          ),
  41         (_BV(13) | _BV(15))
  42 };
  43
  44 /**
  45  * Port names for each DAC port, to be easily accessible by indexing
  46  */
  47 static const enum port_id dac_ports[DAC_PIN_NUM] = {
  48         PORT_ID_DAC1_2,
  49         PORT_ID_DAC1_2,
  50         PORT_ID_DAC3_4,
  51         PORT_ID_DAC3_4,
  52 };
  53
  54 /**
  55  * Command for SPI
  56  */
  57 static uint32_t dac_spi_cmd;
  58 /**
  59  * Shadow variable of SPI command
  60  */
  61 static uint32_t dac_spi_cmd_sh;
  62
  63 int drv_dac_spi_transfer(uint8_t pin, boolean_t enabled, uint16_t value)
  64 {
  65         // Check pin range
  66         if (pin >= DAC_PIN_NUM)
  67                 return -1;
  68
  69         // Check value range
  70         if (value > 4095)
  71                 return -2;
  72
  73         // Prepare command
  74         if (enabled)
  75                 bit_set(dac_pin_status[pin], 12);
  76         else
  77                 bit_clear(dac_pin_status[pin], 12);
  78
  79         dac_pin_status[pin] = dac_pin_status[pin] & 0xF000;
  80         dac_pin_status[pin] |= (value & 0xFFF);
  81
  82         char commands[2];
  83
  84         // Warning!!! Can be "optimized" by compiler
  85         dac_spi_cmd = dac_pin_status[pin];
  86         dac_spi_cmd_sh = dac_spi_cmd;
  87         //--
  88         const struct port_desc *port = &port_desc[dac_ports[pin]];
  89         commands[0] = (dac_spi_cmd_sh & 0xFF00) >> 8;
  90         commands[1] = (dac_spi_cmd_sh & 0xFF);
  91
  92         return port->set(port, commands, sizeof(commands));
  93 }